This invention relates to a leg prosthesis and, more particularly, to a knee joint for a leg prosthesis which is automatically locked when weight is placed on the leg.
Heretofore, attempts have been made to provide artificial legs having mechanical knee joints which are automatically locked and unlocked while the wearer is walking to simulate a natural knee action and walking gait. However, these devices have resulted in rather complex mechanical mechanisms for the knee joint action and have not altogether provided a simplified reliable actuating mechanism for locking the knee joint in a weight supporting configuration. A typical device utilizing a ratchet and pawl mechanism for the knee joint is shown in U.S. Pat. Nos. 2,943,622 and 2,071,711.
An improved operating mechanism for operating a mechanical knee joint is disclosed in applicant's U.S. Pat. No. 4,090,264 which employs a ratchet-type joint and reliable actuating member which are particularly suitable for a heavy person.
Another development for locking a knee joint in a leg prosthesis has been by means of a mechanical clutch released by an electrical control pulse which is derived from the myoelectric activity of the patient's stump. This features enables the amputee to use the artificial leg as a reaction point for his residual muscles. Such a development is disclosed in an article by G. W. Horn entitled "Electro-Control: EMG-Controlled A/K Prosthesis" appearing in Medical and Biological Engineering, Vol. 10, pp. 64-73, Pergamon Press, 1972. However, the user must be trained and skilled in the control of the muscles in his stump to control the knee joint and the knee can only be folded after the mechanism is automatically reset after the leg has been fully extended. Spring force is utilized to position the roller clutch assembly which can vary and thus is lacking in positive, reliable control thereof.
Accordingly, an important object of the present invention is to provide an artificial knee joint for a leg prosthesis which is simplified in construction and reliable in operation.
Yet another important object of the present invention is to provide knee-joint structure for a leg prothesis which has very few moving parts and is lightweight and may be easily incorporated into a lightweight leg prothesis; and which, by virtue of having fewer moving parts, is less susceptible to wear and misadjudgment of the knee joint.
Yet another important object of the present is to provide a knee joint for a leg prothesis employing a mechanical roller clutch assembly which is controlled by positive direct mechanical actuation.
Yet another important object of the present invention is to provide artificial knee joint apparatus having a roller clutch assembly which locks the lower leg from folding when weight is placed on the leg, but otherwise is unlocked to allow the lower leg section to swing in any direction.
Yet another important object of the present invention is to provide artificial knee joint apparatus in employing a roller clutch assembly having a positive locking and unlocking action which allows the lower leg section to be folded anytime there is no weight present upon the foot portion of the prosthesis.
Yet another important object of the present invention is to provide a knee-joint structure for a leg prothesis having an adjustable drag system for controlling the swing speed of the leg.